Many of the electronic devices constituting a variety of electronic appliances are usually manufactured by utilizing the photolithographic technology with the use of a photosensitive resin composition of which the major current in recent years is with the so-called chemical-amplification positive-working photoresist compositions.
It is a recent trend in the field of manufacturing a variety of electronic devices requiring fine working as represented by semiconductor devices that the devices have acquired more and more increased density and degree of integration. This trend leads to an increased demand for the chemical-amplification positive-working photoresist compositions capable of complying therewith.
Along with the trend toward increased fineness in electronic devices, LSIs are required to be of a higher degree of integration and assemblage of such an LSI into an electronic appliance is conducted by way of the multiple-pin thin-film mounting process such as the tape-automated bonding process and the flip-chip process having made their debut.
It is a requirement in the aforementioned multiple-pin thin-film mounting process that protruded electrodes of a 10 μm or larger height or so-called bumps are provided as the connecting terminals on the circuit board. While the bumps are formed in a process in which a barrier metal is stratified on the circuit board bearing an LSI device, a resist film formed thereon is exposed to actinic rays through a photomask of such a pattern as to open the resist film in the points corresponding to the bumps followed by development to give a replica mold which is subjected to plating with an electrode material such as gold and copper followed by removal of the worn-out resist composition and barrier metal, the resist composition used in this process is required to be suitable for the formation of a coating film having a uniform thickness of 20 μm or larger.
In view of the higher density as compared with the cases of the traditional positive-working photosensitive resin compositions containing a quinonediazide compound, on the other hand, it is only in recent years that the chemical-amplification photoresist compositions are highlighted, of which the principal ingredients include a resin capable of changing the solubility in an alkaline solution by interacting with an acid and a photoacid-generating agent capable of generating an acid by irradiation with actinic rays and these resist compositions are also in the major current as a resist composition for the preparation of electronic devices provided with the aforementioned bumps. Accordingly, the demand is increasing for a chemical-amplification positive-working photoresist composition suitable for the formation of a resist film of a large film thickness necessary for bump formation.
Several proposals have been made in this regard including a positive-working radiation-sensitive resin composition for preparation of plated articles containing a photoacid generating agent, a polymer having recurring units represented by the general formula
(in the formula, R1 is a hydrogen atom or a methyl group and R2 is an optionally substituted cycloalkyl group or aryl group having 6 to 20 carbon atoms)and an organic solvent (see JP2001-281862A), a chemical-amplification positive-working photoresist composition for large film thickness containing a photoacid generating agent, a copolymer containing the structural units represented by the general formula
(in the formula, R1 is a hydrogen atom or a methyl group, R2 is a lower alkyl group and X is a group capable of forming a hydrocarbon ring of 5 to 20 carbon atoms together with the carbon atom to which the same is bonded)and an alkali-soluble resin (see JP2004-309775A), a chemical-amplification positive-working photoresist composition for large film thickness containing a photoacid generating agent, a copolymer containing the structural units represented by the general formula
(in the formula, R1 is a hydrogen atom or a methyl group and R2 is an acid-labile group)and an alkali-soluble resin (see JP2004-309776A), a chemical-amplification positive-working photoresist composition for large film thickness containing a photoacid generating agent, and a copolymer containing the structural units represented by the general formula
(in the formula, R1 is a hydrogen atom or a methyl group and R2 is a lower alkyl group)(see JP2004-309778A) and elsewhere.
It is, however, a difficult matter to decrease the defects of the chemical-amplification positive-working photoresist compositions described in the above-cited four patent documents relative to the higher performance required in the current photoresist compositions including the coating adaptability, peelability, development velocity and patterning fidelity as well as the coating adaptability for a large film thickness.